This application is for the support of a research program to investigate the involvement of prostaglandins in the pathogenesis of diseased cells in atherosclerotic arteries. Emphasis will be on the intracellular accumulation of lipid, especially free and esterified cholesterol, in lysosomes and lipid droplets of rabbit aortic cells, during the course of atheromatous transformation. The objectives include investigations contrasting 1. aortic "foam" cells (diseased cells of low density), 2. lipid-enriched aortic smooth muscle cells (diseased cells of high density) and 3. control aortic cells, with respect to 1. the effect of prostaglandins on cholesterol-esterifying activity, 2. the effect of prostaglandins on the integrity of lysosomes and 3. the biosynthesis of prostaglandins E2 and F2 alpha. Cell fractionation by the Metrizamide density gradient centrifugation technique will be employed to separate populations of cells of different lipid contents. Lysosomal latency will be assessed indirectly using fluorometric assays of acid hydrolases, while prostaglandin biosynthesis and cholesterol-esterifying activity will be measured using radioactively labeled fatty acid substrates with subcellular fractions of the cell populations. Gas liquid chromatography will be used to measure intracellular sterol content, while histological and electron microscopical studies will be carried out to assess the pathology of arteries and aortic cells, respectively. These investigations should aid in better understanding the involvement of arterial prostaglandins during the atheromatous transformation of aortic cells to a diseased state.